Recently, televisions which not only receive and display broadcasts but also reproduce and display video contents stored in a memory card and video contents on the network have appeared on the market. Similarly, among mobile devices such as mobile phones, there are products which can display contents obtained from various content providing devices.
In addition, content providing devices have increased in type and number. Examples of such content providing devices include: broadcast systems such as the terrestrial digital broadcast, satellite broadcasting, cable television, and the like; storage media such as hard disks, memory cards, and the like; content providing devices connected to network including content providing sites; and content providing devices connected with multimedia interfaces.
In order to interact with such a variety of content providing devices, a conventional content output apparatus has applications installed therein specific to the respective content providing devices, and the user activates the respective applications. Each of the applications adopts a method of operation, such as content selection, dedicated to the corresponding content providing device. The user operates the respective applications to determine any content from among a large number of contents contained in the content providing devices.
It is troublesome for a user to operate a different application for each of the respective content providing devices. For this reason, Patent Literature 1, for example, discloses a content output apparatus which can unify these applications into a single application, and operate all of the content providing devices in accordance with the respective methods of operation by this single application. The content output apparatus; however, has the following problems.
In the content output apparatus, in order for a user to find a content he/she is interested in from among various contents, the user performs zapping, that is, the user scans through channels by frequently switching between channels in a short period of time. However, such a device that recognizes and utilizes these content providing devices is required to perform various processes such as initializing a corresponding device driver, obtaining data, decoding data, and the like, resulting in a long time for switching between channels.
In addition, as a result of such as recent increasing concern among users about the global environmental issues, it has become important for the content output apparatus to operate with low power consumption. The user performs zapping by switching between contents contained in the different content providing devices by using an integrated interface described above. In this case, delay in switching between the content providing devices can be reduced if the content providing devices are made available beforehand. However, in order to make all of the content providing devices available, power needs to be supplied to all of the devices that use the content providing devices regardless of whether a content which the user desires is contained, resulting in wasted power consumption of the content output apparatus. In contrast, if power is supplied only to the content providing device which is providing a content being currently viewed, power to be consumed by the content output apparatus can be saved. However, time is taken for the above described process during switching between the content providing devices, which leads to delay in switching between the content providing devices. Accordingly, even when the user views contents while performing zapping by switching between the content providing devices, it is desired to switch between the content providing devices without delay and simultaneously save power by eliminating power supply to unnecessary devices.
As one of technologies for solving these problems, there has been a method disclosed by Patent Literature 2. Patent Literature 2 discloses a display device for digital television broadcasting which can switch without delay between channels and save power when zapping is performed by continuously switching between the channels in ascending order or in descending order. The display device for digital television broadcasting performs more processes, when compared with analog broadcasting, such as obtaining data, decoding data, and the like, resulting in delay between a time channel is switched from one to another and the time an image is displayed. A display device of Patent Literature 2 obtains the channel number currently selected and whether the user is performing channel operation in ascending order or in descending order. Subsequently, the display device predicts a channel to be displayed next before the channel is switched to another. Then, the display device starts up a main process system for displaying the corresponding channel and a sub-process system for preparing the predicted channel, thereby switching to the sub-process system at a time when the channel is switched. Accordingly, the display device eliminates delay when the user views channels while performing zapping. Further, the display device stops the operation of the sub-process system when the channel of the main process system is continuously viewed. Accordingly, the display device can reduce power consumption.